Conventionally, a wiper motor with a decelerating mechanism, which has a small size and from which a large output power can be obtained, is adopted as a driving source for a wiper device that is mounted in a vehicle, such as an automobile. This makes it possible to improve mountability of the wiper device in a vehicle body. Further, in order to suppress propagation of electric noises to in-vehicle equipment, such as a radio, a brushless wiper motor that does not have a commutator and a brush may be adopted. Thus, adoption of the brushless wiper motor allows generation of electric noises to be suppressed. Since the brushless wiper motor does not have a commutator and/or a brush, it is possible to improve quietness further, and to reduce a size and a weight thereof.
Japanese Patent Application Publication No. 2013-223317 describes such a brushless wiper motor with a decelerating mechanism, for example. The brushless wiper motor described in Japanese Patent Application Publication No. 2013-223317 includes a motor unit and a decelerating mechanism unit. The motor unit has a yoke, and the decelerating mechanism has a gear housing.
A stator in which a U-phase coil, a V-phase coil, and a W-phase coil are wound is fixed inside the yoke. A rotor is rotatably disposed inside the stator. Further, six magnetic poles of a permanent magnet are embedded inside the rotor. The brushless wiper motor having a so-called interior permanent magnet (IPM) structure is adopted.
On the other hand, the decelerating mechanism, which is composed of a worm and a worm wheel, is housed inside the gear housing. The worm is rotated by the rotor, and thus, turning force with a high torque is outputted from an output shaft of the worm wheel.